Electronic communication devices require power in order to operate. In many cases, these electronic communication devices are deployed in the form of a mobile device, such as a mobile station (MS), with a battery having a limited capacity. In order to extend the operation time of a wireless device, the electronic communication device may enter a reduced power mode, sometimes referred to as a sleep mode, a.k.a., discontinuous reception (DRX). This sleep mode is designed to reduce the power consumption of the electronic communication device while the electronic communication device is not active. The reduction of the electronic communication power consumption through a sleep mode extends the life of the battery and reduces the amount of heat produced by the device without disabling the device.
To this end, three power saving schemes are defined for sleep mode in the IEEE 802.16e standard power saving class (PSC). PSC type I is for connections of best efforts (BE) and non-real-time variable rate (NRT-VR) type application. PSC type II is for connections of unsolicited grant service (UGS) and real-time variable rate (RT-VR) type applications. PSC type III is for multicast connections as well as for management operations.
With PSC type I, sleep windows (or sleep intervals) are interleaved with listening windows (or listening intervals) of a fixed duration. If there is no traffic as indicated by a traffic indication message, such as an MOB_TRF_IND(0) message, the sleep interval in the next discontinuous reception (DRX) cycle doubles until the sleep interval reaches a predetermined upper limit. If the Traffic_triggered_wakening_flag (TTWF) is ‘1’ (i.e., TTWF=1), the MS returns to normal operation (i.e., active mode) upon receiving an MOB_TRF_IND(1) message. The MOB_TRF_IND(1) message indicates to the MS that there is DL data traffic ready to be transmitted to the MS. If TTWF=0, power saving class is not deactivated if traffic appears. In other words, data traffic is allowed in sleep mode if TTWF=0. However, data traffic is transmitted only in listening intervals, which are of a fixed short duration. The MS also automatically returns to normal operation whenever the MS has UL data ready for transmission.
With PSC type II, all sleep windows are of the same size, and interleaved with listening windows of a fixed duration. Similar to PSC type I, the MS exits Sleep Mode when the MS needs to or is instructed by a base station (BS) to do so. For PSC types I and II, the definition of sleep and listening windows and the activation of Sleep Mode require sending MAC messages (e.g., MS initiated MOB_SLP-REQ, (bandwidth request) BR, or UL Sleep Control messages; and BS initiated MOB_SLP-RSP message or DL Sleep Control Extended Subheader). The deactivation of Sleep Mode requires a BS to send an MOB_TRF-IND message with a positive indicator when TTWF=1. Alternatively, MAC message RNG-REQ also can be used to define, activate and deactivate Sleep Mode as well.
With PSC type III, signaling methods for defining and activating sleep window are the same as PSC types I and II. The difference is that the deactivation of Sleep Mode occurs automatically at the end of a sleep window (i.e., each sleep cycle lasts just one time period and one sleep window needs one definition/activation) with PSC type III.
Using the above power saving schemes, when TTWF=1, the MS has to leave the sleep mode for data traffic delivery regardless if the data traffic is for DL or UL. For light bursty traffic, the MS may go back and forth between active mode and sleep mode frequently. This results in a significant exchange of MOB_SLP_REQ/RSP messages (i.e., a high signaling overhead).
When TTWF=0, the MS could receive data without leaving sleep mode. However, the disadvantage is that the MS can only receive data in the listening interval. Consequently, the remaining data has to be transmitted in the following listening intervals. Moreover, the sleep interval still doubles even though there is positive traffic indication.
Thus, the above power saving operations are more concerned with packet latency than power saving performance in sleep mode as the definition, activation, deactivation and reactivation of discontinuous reception (DRX) are all driven by signaling. Accordingly, a significant amount of signaling overhead would be invoked if a power saving configuration were to adapt to changing MS traffic pattern and activity level using the above power saving operations. This high signaling overhead requires considerable power to maintain the sleep state of the traditional communication system. As a consequence, this high signaling overhead requires considerable power and has a corresponding drain upon the battery life of the device.
Accordingly, there is a need in the art for a system and method that effectively handle the sleep mode to adapt to changing MS traffic pattern and activity level. In particular, there is a need for a system and method for effectively handling the sleep mode that effectively reduce power consumption by adapting to changing MS traffic pattern and activity level without an increase in signaling overhead.